Which of the following pairs of symbols represent atoms that are isotopes of each other?

• A. 16O and 16N
• B. 12C and 14C
• C. 23Na and 24Mg
• D. 35Cl and 35S

Answer: (B)

Verified step by step guidance

1. Recall that isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means isotopes have the same atomic number but different mass numbers.
2. Identify the atomic number (number of protons) for each symbol in the pairs. The atomic number is determined by the element symbol (e.g., O for oxygen has atomic number 8, N for nitrogen has atomic number 7, C for carbon has atomic number 6, Na for sodium has atomic number 11, Mg for magnesium has atomic number 12, Cl for chlorine has atomic number 17, and S for sulfur has atomic number 16).
3. Compare the atomic numbers in each pair to see if they are the same. If the atomic numbers differ, the atoms are not isotopes because they are different elements.
4. For pairs with the same atomic number, check if the mass numbers (the superscript numbers) are different. If so, these pairs are isotopes because they have the same number of protons but different numbers of neutrons.
5. Conclude which pair represents isotopes based on the above criteria.